- var_dump: documentation ( source)
<?php
var_dump(new DateTime('2015-08-31T00:55:00.000Z'));
var_dump(new DateTime('2015-08-31T00:55:00.000'));
var_dump(new DateTime('2015-08-31T00:55:00'));
var_dump(new DateTime('2015-08-31T00:55'));
var_dump(new DateTime('2015-08-31'));